This leaves me wondering what would happen if you attached a coupling to a trumpet and ran the sound through an effects/feedback box. Why should electric guitars have all the fun?
The difference with electric guitars is that guitar pickups are relatively sensitive and then go through multiple stages of amplification, which makes the system ripe for feedback loops.
Some saxophone players have been known to generate feedback through on-board microphones. Strictly speaking, this isn't exciting the horn, but it does introduce feedback that's excited BY the instrument.